Apparatus and method for forming a screw flight

ABSTRACT

This invention relates to an apparatus for forming a helical screw flight from a flight blank. The apparatus includes a base and an engaging means. The engaging means is movably mounted to the base and is configured to formingly engage the blank so as to form a twist in at least a portion of the flight blank corresponding to a predetermined pitch of the flight.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/130,837, filed Mar. 27, 2014, which is a national stage applicationfiled under 35 U.S.C. 371 of International Application No.PCT/AU2012/000803, filed Jul. 5, 2012, which claims priority fromAustralian Patent Application No. 2011902667, filed Jul. 5, 2011, eachof which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

This invention relates generally to the field of materials handlingequipment. More particularly, the present invention relates to screw orauger flights (particularly sectional flights) and to an apparatus andmethod of forming such flights.

BACKGROUND OF THE INVENTION

Any discussion of the prior art throughout the specification should inno way be considered as an admission that such prior art is widely knownor forms part of common general knowledge in the field.

Screw or auger flights are typically used in bulk handling industriesfor efficiently moving fluid, granular or semi-solid material. Rotationof the flight causes the material to be conveyed along the surface of aspiraled coil section.

The means and method of manufacturing conventional sectional screwflights involves pressing each section of flight between a set ofappropriately shaped dies. Each section of flight is then typicallywelded to a shaft in sequence to form a complete conveyor screw.

The conventional die pressing method has a number of inherentdisadvantages. These disadvantages include that, depending on thethickness of the blank material used, is it often necessary to repeatthe die pressing operation several times in order to conform the shapeof the annulus to the shape of the dies between which the blank ispressed. The requirement to repeat the pressing cycle necessarily addsto the costs of production of screw flights produced via this method.

Furthermore, the blank typically undergoes plastic deformation duringthe pressing process which can lead to inaccuracy in flight profilesoutside of desired manufacturing tolerances. Such variations away frothdesired manufacturing tolerances necessarily lead to inferior productsand a resulting reduction in product performance and lifespan.

In addition, for each particular size and pitch for a flight, two setsof dies are needed if both left and right hand flights are to beproduced, further adding to the costs of using dies to form screwflights.

It is also difficult to produce accurate dies which will produce aflight of a particular size and pitch. Accordingly, it is typicallynecessary to use an iterative process of trial and error whereby severalsets of dies are produced, tested and modified until the desiredproperties of a flight can be achieved from the die set.

It is an object of the present invention to overcome or ameliorate oneor more of the disadvantages of the prior art, or at least to provide auseful alternative.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided anapparatus for forming a helical screw flight from a flight blank, theapparatus including:

a base; and

engaging means movably mounted to the base, the engaging means beingconfigured to formingly engage the blank so as to form a twist in atleast a portion of the flight blank corresponding to a predeterminedpitch of the flight.

Preferably, the flight blank is in the form of an annulus, morepreferably, an open ended annulus (e.g. a penannular) wherein theannulus shaped blank has an inner diameter and an outer diameter. Theengaging means is preferably adapted to twist the portion of the annulusabout a mean radius line of the annulus. It will be appreciated by thoseskilled in the art that, by twisting the blank about its mean radiusline, undesirable rounding or rolling across the cross-section of theblank is substantially avoided.

The engaging means preferably engages opposed sides of the blank suchthat forming movement of the engaging means forms a twist in at least aportion of the flight blank.

In some embodiments, the engaging means includes primary engaging meansfor engaging the blank at at least two spaced apart positions, wherebythe primary engaging means is configured to cause relative movementbetween the at least two engaged positions so as to form the twist inthe blank.

In certain preferred embodiments, the primary engaging means includestwo pairs of (primary) side plates. Each side plate is preferably a dieformed plate having an engaging portion such as, for example, anengaging edge or surface for engaging the blank. Each side plate ispreferably arranged so as to extend in a direction which issubstantially normal to the mean radius line of the blank.

Preferably, each pair of side plates has a first fixed plate and asecond movable plate, the second plate being movable relative to thefixed plate.

In some preferred embodiments, the engaging means includes secondaryengaging means for engaging the blank at at least one position inbetween the primary engaging means. The secondary engaging meanspreferably engages the blank at a central or mid-point between theprimary engaging means. Preferably, the secondary engaging meansincludes a pair of mid-plates. The mid-plates preferably include a fixedmid-plate and a movable mid-plate, the movable mid-plate being movablerelative to the fixed mid-plate.

The fixed plates of both the primary and secondary engaging means arepreferably mounted to a mounting means such as a mounting frameconnected to the base. Preferably, the mounting means includes areceiving formation for receiving each fixed plate. The receivingformation preferably includes a pair of spaced apart channels, grooves,slots, ridges, or other suitable formation for receiving the fixed sideplates, and a central receiving formation (e.g. channel) for receivingthe fixed mid-plate.

Preferably, each fixed plate has a mounting formation for mounting theplate in or on or otherwise to the receiving formation. The mountingformation of each plate is preferably complementary in shape to that ofthe receiving formation. For example, the mounting formation and thereceiving formation may be configured as a tongue-and-groove typearrangement.

In certain embodiments, securing means is provided for securing eachfixed side plate in position, relative to the mounting means. Thesecuring means preferably includes one or more locking screws forholding the mounting formation (e.g. tongue) in the associated channel.Preferably, each receiving formation is configured to enable theassociated fixed plate to be selectively mounted at a desired orpredetermined position along the length of the receiving formation. Forexample, the fixed plates can be slid along the associated channel andthen locked in the desired position.

Preferably, a locking means such as, for example, a lock-bolt isprovided for locking the fixed mid-plate in position, relative to themounting means.

The movable plates of the primary engaging means and the secondaryengaging means are preferably mounted to a movable frame, the framebeing movably mounted to the base to enable relative movement betweenthe fixed plates and the movable plates.

The movable frame preferably has a mounting formation for mounting themovable plates. Preferably, the mounting formation of the movable framecorresponds to (e.g. mirrors) the mounting formation of the fixedmounting frame such that the engaging portion of each pair of fixed andmovable plates is substantially aligned. That is, the pairs of sideplates and the pair of mid-plates are preferably in engaging alignment.

The receiving formations are preferably arranged such that the pairs ofside plates are angled relative to one another. Preferably, the sideplates are configured such that the relative angle therebetween is lessthan 180 degrees. In certain preferred embodiments, the side plates arearranged to have an angle of approximately 60 degrees therebetween. Itwill be appreciated that the primary engaging members are not limited tobeing angled at 60 degrees, but could, in other embodiments, be angledat any suitable angle less than 180 degrees. For example, the sideplates can be angled at approximately 30, 45, 65, 75, 90, 105, 120, 135or 145 degrees relative to each other.

Preferably, a support means is associated with the side plates forsupporting the flight blank, in use. The support means is preferablyconfigured to support the outer diameter of the blank. Preferably, thesupport means includes a first support bracket mountable to a fixed sideplate of a first pair of primary engaging side plates and a secondsupport bracket mountable to a movable side plate of a second pair ofprimary engaging side plates. Each support bracket is preferablyselectively adjustably positionable relative to the associated sideplate and secured thereto by a suitable locking means such as one ormore locking elements (e.g. screws). It will be appreciated that thesupport brackets can be selectively mounted to the desired side plates,depending on whether a right-hand or left-hand helical screw flight isto be formed by the apparatus.

The moveable frame is preferably moved by an actuating means. Theactuating means preferably includes a hydraulically driven cylinder, thehydraulic cylinder being selectively movable between an extendedposition and a retracted position for moving the movable frame and thusthe movable plates of the primary and secondary engaging means.Preferably, the hydraulic cylinder has a cylinder rod which isconfigured to cause linear movement of the movable frame when thecylinder rod extends or retracts.

To facilitate the forward and backwards linear movement of the movableframe, the movable frame and base are preferably fitted with guidemeans. Preferably, the guide means includes at least one front guide barand at least one rear guide bar extending from the movable frame. The atleast one front guide bar is arranged to pass through an aperture in afront guide plate and the at least one rear guide bar is arranged topass through an aperture in a rear guide plate. In one particularlypreferred embodiment, there is provided two front guide bars and tworear guide bars.

Preferably, a first pair of side plates is configured to rotate theportion of the blank between that pair of side plate and the mid-plate(i.e. secondary engaging means) in a clockwise direction, and a secondpair of side plates is configured to rotate the portion of the blankbetween that pair of side plates and the mid-plate in acounter-clockwise direction, or vice versa. Again, it will beappreciated that side plates can be mounted to achieve the desireddirection of rotation for producing either a right-hand or left-handtwist in the blank.

Each side plate (fixed and movable) is generally trapezoidal in shape,wherein its engaging edge is tapered relative to its mounting formation.To achieve the desired rotation of the blank at the point held betweenthe side plates, the first pair of side plates are arranged such thatthe tapered edges of the fixed and movable plates in the first pair aresubstantially parallel and extend at a negative angle (or positive anglefor opposite hand formation). Similarly, the second pair of side platesare arranged such that the tapered edges of the fixed and movable platesin the second pair are substantially parallel and extend at a positiveangle (or negative angle for opposite hand formation).

It will therefore be appreciated that, due to the tapered engaging edgesof the side plates, the relative linear movement between the fixed andmovable side plates results in a rotation of the part of the blankbetween the plates about the mean radius line to produce the desiredtwist in the blank.

In at least one preferred embodiment, the actuating means is configuredsuch that the apparatus operates with a forming force in the range of 0to 60 tonne at 200 bar (2,900 psi), and the forming speed is within therange of 0 to 80 mm/s. Embodiments operating within these parameters canbe suitable for forming a helical screw from a blank having a thicknessin the range of 1 mm to 300 mm.

According to a second aspect of the invention, there is provided amethod of forming a helical screw flight, the method including:

providing a flight blank of a predetermined size; and

formingly engaging the blank so as to form a twist in at least a portionof the flight blank, the twist substantially corresponding to apredetermined pitch of the flight.

Preferably, the method includes twisting at least a portion of the blankgenerally about a mean radius line of the blank.

Preferably, the method includes engaging the blank with primary engagingmeans at at least two spaced apart positions, whereby the primaryengaging means is configured to cause relative movement between the atleast two engaged positions so as to form the twist in the blank.

The method preferably includes using a secondary engaging means forengaging the blank at at least one position in between the primaryengaging means, whereby the engaged portion of the blank on one side ofthe secondary engaging means is twisted in a first direction and theengaged portion of the blank on the other side of the secondary engagingmeans is twisted in a second opposed direction.

Preferably, the method includes determining the size of the blank fromat least one of a desired pitch, outer diameter, inner diameter, andthickness of the formed helical screw flight.

According to a third aspect of the invention, there is provided a screw(or auger) flight which has been manufactured in accordance with themethod of the second aspect of the invention.

According to a fourth aspect of the invention, there is provided amethod of setting up an apparatus for forming a helical screw flightfrom a flight blank, the method including:

securing a central engaging means to the apparatus;

aligning a set up device with the central engaging means;

securing the set up device to the central engaging means in the alignedposition;

determining a position for mounting side engaging means relative to thecentral engaging means with the set up device; and

securing the side engaging means to the apparatus at the determinedposition.

In some preferred embodiments, the method of setting up the apparatusfurther includes determining the position at which a support′bracket isto be secured relative to the side engaging means; and securing thesupport bracket at the determined position for supporting the flightblank, in use.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described, by way ofexample only, with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of an apparatus for forming a helical screwflight according to the invention;

FIG. 2 is a plan view of the flight forming apparatus of FIG. 1;

FIG. 3 is a left side view of the apparatus;

FIG. 4 is a front elevation of the apparatus;

FIG. 5 is a plan view of the apparatus with the sheet metal panel coverremoved;

FIG. 6 shows an annulus shaped flight blank;

FIG. 7 is a side view of a formed helical screw flight;

FIG. 8 is a view of the formed flight of FIG. 7 from another side;

FIG. 9 shows the fixed mounting frame of the apparatus with themid-plate fixed in position, and a set-up rule assembly mounted to themid-plate;

FIG. 10 is an enlarged view of the mid-plate of FIG. 9, showing thealignment with the rule-assembly;

FIG. 11 shows the base offset between each fixed side plate and themid-plate, and the support offset for a support bracket mounted to aside plate;

FIG. 12 is an enlarged view of a rule guide used with rule-assembly forsetting the base offset;

FIG. 13 is a perspective view of the rule guide of FIG. 12;

FIG. 14 is schematic view showing setup of the fixed side plates;

FIG. 15 is an enlarged side view of FIG. 14;

FIG. 16 is a perspective view showing setup of the a support bracket;

FIG. 17 is an enlarged view of the support bracket setup of FIG. 16;

FIG. 18 is a side view of the engaging means showing the primary andsecondary engaging plates in forming engagement with the blank;

FIG. 19 is a side view of the engaging means with the hydraulic cylinderin a partially extended position such that a roll gap exists between thefixed and movable plates to enable manipulation of the blank;

FIG. 20 is a side view of the engaging means with the hydraulic cylinderin its retracted position to enable insertion of a blank and extractionof a formed flight; and

FIG. 21 is a side view of a side engaging plate.

PREFERRED EMBODIMENTS OF THE INVENTION

Referring to the drawings, the invention provides an apparatus 1 forforming a helical screw flight 2 from an open ended annulus shapedflight blank 3. As most clearly shown in FIG. 6, the annulus shapedblank 3 has an inner diameter and an outer diameter.

The size of the blank 3 is calculated from the values of the desiredproperties of the helical flight 2 including the inner and outerdiameters of the flight 2, the pitch of the flight (FIG. 7) and thethickness of the material used to form the blank/flight (FIG. 8). Itwill be appreciated by those skilled in the art that the inner and outerdiameters of the blank 3 are necessarily greater than those of theformed flight 2.

The flight forming apparatus 1 has a base 4 for resting the apparatus 1on a supporting surface such as a workshop floor (not shown).

The apparatus 1 includes a mounting means in the form of a mountingframe 5 fixedly connected to the base 4. The fixed mounting frame 5 isconfigured for mounting a fixed engaging means in the form of two spacedapart side plates 6 and a central or fixed mid-plate 7. As will bedescribed in further detail below, the fixed side plates 6 and the fixedmid-plate 7 are arranged to engage respective spaced apart positions ona first side surface 8 of the flight blank 3.

The fixed mounting frame 5 includes a mounting plate 9 having areceiving formation in the form of three channels 10 for selectively andreleasably receiving each fixed plate (6, 7). The channels 10 include apair of spaced apart side channels for receiving the fixed side plates 6and a central channel for receiving the fixed mid-plate 7.

As most clearly shown in FIG. 9, the side channels 10 are symmetricallyarranged on either side of the central channel and extend radially at anangle of approximately 60 degrees relative to each other. The sideplates 6 and mid-plate 7 can be inserted into and slid along therespective channels 10 to a desired position so as to suit a particularsize flight blank 3 and desired pitch of the flight 2.

To engage the opposite second side 11 of the blank 3, the apparatus 1further includes movable engaging means mounted to a movable frame orcarriage 12. The carriage 12 is adapted for relative linear slidingmovement with respect to the fixed frame 5.

The carriage 12 has a mounting plate 13 with a receiving formation inthe form of three channels 14 for selectively and releasably receivingthe movable engaging means.

The movable engaging means is in the form of two movable side plates 15and a movable mid-plate 16. The channels 14 of the movable mountingplate 13 are arranged to correspond with (or mirror) the channels 10 ofthe fixed mounting plate 5.

The two pairs of side plates (6, 15) together for a primary engagingmeans and the pair of mid-plates (7, 16) form a secondary engaging meansof the apparatus.

The side and mid-engaging plates (fixed and movable) are preferably dieformed components having an engaging edge 17 for engaging the respectivesurfaces of the blank 3. Each engaging plate is configured so that whenit is inserted into its associated channel the engaging edge 17 extendsradially, relative to the flight blank 3, so as to be substantiallynormal to the mean radius line of the blank 3.

As most clearly shown in FIG. 21, each side plate (fixed and movable) isgenerally trapezoidal in shape and has a mounting formation in the formof a stepped or tongue-shaped edge 18 which can be received in therelevant side channel (10, 14) of the fixed or movable mounting plate(5, 13). The engaging edge 17 is tapered relative to the mountingformation so as to extend at a predetermined die plate angle ‘α’relative to the mounting edge 18. The die plate angle ‘α’ is calculatedto suit the desired pitch of the flight 2. Accordingly, it will beappreciated that sets of engaging plates with various die plate angles‘α’ can advantageously be manufactured and used, interchangeably, asrequired to manufacture helical flights 2 of various pitches.

In order to achieve the desired rotation (twist) of the blank 3 at thepoints held between the side plates, one pair of side plates arearranged such that the tapered edges 17 of the fixed and movable platesin this pair are substantially parallel and extend at a negative angle.Similarly, the second pair of side plates is arranged such that thetapered edges 17 of the fixed and movable plates in this pair aresubstantially parallel and extend at a positive angle.

It will therefore be appreciated that, due to the tapered engaging edges17 of the side plates, the relative linear movement between the fixedand movable side plates results in a rotation of the part of the blankbetween the side plates about the mean radius line to produce thedesired twist in the blank. In the figures, the front pair of sideplates extend at a negative angle and are therefore configure to rotatethat portion of the blank in a counter-clockwise direction. The rearpair of side plates extend at a positive angle and are thereforeconfigure to rotate that portion of the blank in a clockwise direction.It will of course be appreciated by those skilled in the art that theplates can be readily interchanged so the front and rear pairs of sideplates extend at opposite angles to produce a flight of different hand(e.g. a left or right hand flight).

To secure the mid-plates (7, 16) in position, a locking means in theform of a lock-bolt (FIG. 9) is provided for locking the mid-platesrelative to the respective mounting plates (9, 13).

With reference to FIGS. 9 to 17, once the mid-plates (7, 16) aresecurely locked in position, a set up device having a mounting bracket19 and a pair of oppositely directed rulers 20 is mounted on themid-plate (7, 16). The set up device is used to determine the correctpositioning of the side plates (6, 15) in their respective sidechannels, relative to the mid-plate. As best seen in FIG. 11, theengaging edge 17 of the side plates are positioned at a predeterminedbase offset distance from the mid-plate. As the side plates (6, 15) areoppositely tapered, the side plate on the right of FIG. 11 is sliddownwardly along its channel (10, 14) until its engaging edge 17 meetsthe ruler 20 at the base offset distance. Due to the opposite taper, theside plate on the left of FIG. 11 is slid upwardly along its channel(10, 14) until its engaging edge 17 meets the ruler 20 at the baseoffset distance.

The side plates (6, 15) are secured in position in the respectivechannels (10, 14) by securing means in the form of a plurality oflocking screws 21. The locking screws 21 pass through holes 22 in theside wall 23 of the channel and securingly engage the mounting tongue 18of the associated side plate (6, 15). In the illustrated embodiment, asbest seen in FIG. 11, seven locking screws 21 are used to secure eachside plate (6, 15).

Referring again to FIG. 11, a support means in the form of a pair ofsupport brackets 24 is provided for supporting the flight blank 3, inuse. One support bracket 24 is attached to the fixed side plate of thefirst pair of primary engaging plates and a second support bracket isattached the movable side plate of the second pair of primary engagingplates. The support brackets 24 are selectively adjustably positionablerelative to the associated side plate and secured thereto by a suitablelocking means in the form of locking bolts 25. In the illustratedembodiment, three locking bolts 25 are used to secure the supportbracket 24 to the associated side plate (6, 15). As most clearly shownin FIG. 21, the side plates (6, 15) have three apertures 26 throughwhich the locking bolts 25 pass to hold the support bracket 24 relativeto the side plate (6, 15).

The apparatus 1 further includes an actuating means in the form of ahydraulically driven cylinder 27 having a cylinder rod 28 coupled to thecarriage 12. The coupling arrangement is such that movement of thecylinder rod 28 causes a corresponding linear movement of the carriage12. The movement of the cylinder rod 28 is selectively controllablebetween an extended position and a retracted position so as to controlthe relative spacing between the fixed and movable plates of the primaryand secondary engaging means.

To facilitate the forward and backwards linear movement of the movableframe 12 and, in particular, to enhance the accuracy of this movement,front and rear guide bars 29 are fitted to and extend from the carriage12. The front and rear guide bars 29 are arranged to slidably passthrough guide sleeves 30 fixed on or relative to the base 4.

In use, the apparatus 1 is initially started with the cylinder rod 28 inits retracted position to enable a new flight blank 3 to be placedbetween the fixed and movable engaging plates (6, 7, 15, 16). Thecylinder rod 28 is then extended to move the carriage 12 to anintermediate position between the fully retracted and extendedpositions. In the intermediate position, the blank 3 can be supported onthe support brackets 24.

The cylinder rod 28 is then actuated to extended at a predeterminedforming speed to bring the side and mid-plates into forming engagementwith the respective surfaces (8, 11) of the blank 3. The plates areconfigured such that the front pair of side plates rotate the portion ofthe blank between that pair of side plates and the mid-plates in acounter-clockwise direction, and the rear pair of side plates isconfigured to rotate the portion of the blank between that pair of sideplates and the mid-plates in a clockwise direction.

As the engaging plates extend substantially normal to the mean radiusline of the annulus, the rotation induced by the engaging plates forms atwist in the engaged portion of the annulus about the mean radius lineof the annulus. It will be appreciated by those skilled in the art that,by twisting the blank about its mean radius line, undesirable rounding,coning or rolling across the cross-section of the blank is substantiallyavoided.

Once the form twisting process has been done, the cylinder rod 28 isretracted to its intermediate position and the blank 3 is rolled on thesupport brackets 24 to bring the next section of blank into position andthe forming process is repeated. These steps are repeated until theentire blank 3 has been twisted and the helical flight 2 is complete.

Accordingly, the present invention in various embodiments thus overcomesa number of problems and provides a number of advantages. Preferredembodiments of the invention provide an efficient apparatus for forminga helical screw flight which, due to the use of interchangeable engagingplates, enables flights of various sizes, pitches and hands to bereadily formed in a cost effective manner. The interchangeable platesalso provide advantages in terms reduced tooling costs as sets of platescan be produced and used as desired. Set-up times are also reduced withfurther associated cost saving advantages through the reduction in themanual labour input required. By engaging the blank in a radial manner,the apparatus advantageously forms the desired twist in the blank aroundthe mean radius line without plastically working the blank. The radialengagement also advantageously inhibits undesirable rolling, rounding orconing of the edges which can adversely affect material transfer andflow rates. Preferred forms of the apparatus are easy to install, set upand use and provide improvements in accuracy to design requirements. Inthese and other respects, the invention in its preferred embodiments,represents a practical and commercially significant improvement over theprior art.

Although the invention has been described with reference to specificexamples, it will be appreciated by those skilled in the art that theinvention may be embodied in many other forms.

1.-16. (canceled)
 17. A method of setting up an apparatus for forming ahelical screw flight from a flight blank, the apparatus being of thetype having a first mounting frame and a second mounting frame movablerelative to each other, wherein the method includes the steps of:mounting a first central forming plate to the first mounting frame suchthat a first central forming edge of the first central forming plate isspaced from the first central forming plate by a first predetermineddistance; mounting a first left side plate to the first mounting framesuch that a first left forming edge of the first left side plate extendsat an angle relative to the first central forming edge; and positioningthe first left side plate such that a portion of the first left formingedge is also spaced from the first central forming plate by the firstpredetermined distance.
 18. The method according to claim 17, includingthe step of: positioning the first left side plate such that a centrepoint of the first left forming edge is spaced from the first centralforming plate by the first predetermined distance.
 19. The methodaccording to claim 17, including the step of: positioning the first leftside plate such that the portion of the first left forming edge isarranged at a predetermined base or lateral offset distance from thefirst central forming edge.
 20. The method according to claim 17,including the step of: positioning the first left side plate such thatthe portion of the first left forming edge is arranged at apredetermined distance along a first left receiving formation of thefirst mounting frame relative to an apex formed between axis of thefirst central forming edge and the first left receiving formation. 21.The method according to claim 17, including the step of: mounting afirst right side plate to the first mounting frame such that a firstright forming edge of the first right side plate extends at an anglerelative to the first central forming edge, wherein the line along whichthe first left forming edge and the first right forming edge meet at anapex; and positioning the first right side plate such that a portion ofthe first right forming edge is also spaced from the first centralforming plate by the first predetermined distance.
 22. The methodaccording to claim 17, including the step of: mounting a second centralforming plate to the second mounting frame such that a second centralforming edge of the second central forming plate is spaced from thesecond central forming plate by a second predetermined distance;mounting a second left side plate to the second mounting frame such thata second left forming edge of the second left side plate extends at anangle relative to the second central forming edge; and positioning thesecond left side plate such that a portion of the second left formingedge is also spaced from the second central forming plate by the secondpredetermined distance.
 23. The method according to claim 22, includingthe step of: positioning the second left side plate such that a centrepoint of the second left forming edge is spaced from the second centralforming plate by the second predetermined distance.
 24. The methodaccording to claim 22, including the step of: positioning the secondleft side plate such that the portion of the second left forming edge isarranged at a predetermined base or lateral offset distance from thesecond central forming edge.
 25. The method according to claim 22,including the step of: positioning the second left side plate such thatthe portion of the second left forming edge is arranged at apredetermined distance along a second left receiving formation of thesecond mounting frame relative to an apex formed between axis of thesecond central forming edge and the second left receiving formation. 26.The method according to claim 22, including the step of: mounting asecond right side plate to the second mounting frame such that a secondright forming edge of the second right side plate extends at an anglerelative to the second central forming edge, wherein the line alongwhich the second left forming edge and the second right forming edgemeet at an apex; and positioning the second right side plate such that aportion of the second right forming edge is also spaced from the secondcentral forming plate by the second predetermined distance.
 27. Themethod according to claim 17, including the step of: providing a set updevice with at least one rule; positioning the set up device relative tothe first mounting frame, thereby to facilitate the positioning of thefirst left side plate such that the first left forming edge is arrangedin the desired position relative to the first central forming edge. 28.The method according to claim 27, wherein the set up device includes amounting bracket and a pair of oppositely directed rulers extendinglaterally from the mounting bracket, and the method further includes thesteps of; securing the set up device via the mounting bracket to thefirst central forming plate such that the first left forming edge can bemoved into engagement with the respective rule so as to position firstleft side plate relative to the first mounting frame.